The electrical and material properties of MOS capacitors with electrolessly deposited integrated copper gate

The electrical properties of electroless-deposited barriers were studied us ing metal-oxide-silicon (MOS) capacitors with thin (14 nm) thermal oxide. T hree different metal electrodes were deposited on a thin sputtered Co seed layer: (a) sputtered Al, (b) electroless Co(W,P) and (c) electroless multil ayer of Co(W,P)/Cu/Co(W,P). The study includes thermal stress in vacuum in the 300-600 degreesC temperature range, for periods of 30 min to 4 h, follo wed by electrical characterization. The high-frequency capacitance versus v oltage (C-V) characteristics of the capacitors was near ideal after anneali ng at 300-500 degreesC for 30 min. After annealing at higher temperatures f or longer times the inversion capacitance increased above the ideal high-fr equency value while the flat band voltage remained unchanged. The minority carrier Lifetime, as obtained from transient capacitance analysis, was in t he range of 60 mus for samples annealed at temperatures below 500 degreesC. It dropped for the samples with copper layers to 12 mus after 520 degreesC anneal for 2 h and to 1 mus after 600 degreesC for 4 h while remaining in the range of 50-60 mus for the samples with either electroless barrier or a luminum. AES profiling indicated that the copper profile remained unchanged after annealing at temperatures up to 500 degreesC anneal for 30 min. Abov e 520 degreesC, the copper profile showed significant diffusion onto the Co (W,P) barrier layer underneath and much less diffusion onto the Co(W,P) cap ping layer above. (C) 2001 Elsevier Science B.V. All rights reserved.